1. Field of the Invention
The present invention relates to a fiber drum made mainly of a paper material, a cylindrical body of the paper material constituting the fiber drum, and a method of fabricating the cylindrical body.
2. Prior Art of the Invention
One of such conventional cylindrical bodies of a fiber drum is illustrated in FIG. 13. The cylindrical body consists mainly of a roll B of a paper sheet S having a bottom at one end. The roll B has an opening C thereof at the other end and an edge thereat is inwardly curled together with a metal ring E thus forming an inwardly curled rim F.
The metal ring E has an inward rib G at an intermediate portion thereof projected substantially 10 mm inwardly of the roll B.
As the cylindrical body A has the paper sheet S and the metal ring E curled together, its curled rim F will particularly require more labor and time to be disassembled during a recycling process. Also, the rim F has to be further separated into the metal ring E and the paper sheet S with extra labor. Once an amount of powder or grains is directly loaded into the fiber drum with no use of any inner bag, a portion of the powder or grains may be trapped by the inward rib G and the inwardly curled rim F of the cylindrical body A, and thus be failed to be removed from the drum.
We, the inventors, have proposed a modified fiber drum disclosed in Japanese Patent Laid-open Publication 2000-185724 as shown in FIG. 14. A cylindrical body A2 of the fiber drum shown in FIG. 14 comprises a roll B2 having a cylindrical shape and made of simply a paper material with an adhesive. The roll B2 in its vertical position has outwardly curled portions I and J provided on both, upper and lower, ends thereof at openings. The cylindrical body A2 is accompanied with a cover plate K and a bottom plate L both made of a paper material, hence constituting a fiber drum D. The cover plate K consists mainly of a top portion M having a disk shape and a rim portion N extending perpendicularly from the top portion M for being detachably joined to the upper curled portion I of the cylindrical body A2. The bottom plate L consists mainly of a bottom portion O having a disk shape and a rim portion P extending perpendicularly from the bottom portion O and bonded by an adhesive to the lower curled portion J. The drum is filled with desired objects and then sealed at the joint between the rim portion N of the cover plate K and the roll B2 with a length of sealing tape (not shown). Accordingly, the fiber drum D using no metal material can easily be disassembled. Also, as the cylindrical body A2 has no projection on its inner side, contents such as powder can be completely removed with no residue remaining in the drum.
However, the body B2 of the fiber drum D shown in FIG. 14 has its inner side turned over the outer side for forming the curled portions I and J. As the material of the inner side is pulled radially of the opening at each end, the curled portion I or J may have a flaw. The flaw will then result in the generation of paper dust. For compensation, the curled portions I and J after formed are often coated at their surfaces with a resin material or the like. This will result in extra labor and cost.